It is not uncommon for today's wireless devices to have multiple transceivers, each of which supports a different Radio Access Technology (RAT). Some of such RATs include Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS), Universal Mobile Telecommunications System (UMTS), and WiFi. Likewise, it is not uncommon to find overlapping coverage areas that support multiple RATs operating on widely-separated carrier frequencies. In such areas, wireless devices equipped with multiple radios are able to access multiple RAT networks, and to also choose between them.
However, various RATs currently operate independently in today's wireless-enabled communications environment. For example, a user of a multi-radio wireless device may selectively elect to operate either in a WiFi mode or in a cellular mode, but cannot combine both for a common service, even if both RATs are available at the user's location. Furthermore, a radio signal associated with each RAT may experience uncorrelated, high-variability in link quality due to propagation loss, fading and interference.
While radio link quality is generally robust for most types of applications ranging from delay-sensitive to delay-tolerant, it is not uncommon to experience outages, manifested by dropped calls or transmission errors. Moreover, it is not currently possible to achieve greater reliability of the radio link by introducing greater redundancy in the transmitted signal due to limitations imposed by the wireless channel characteristics (e.g., the channel impairments are likely to be correlated). As a result, the level of achievable reliability is limited when using a single radio link.